Factsheet: Modelled vs. 'Real' data

Data presented on LAWA at a site, catchment and regional level is data collected by council and NIWA scientists in the field. At a national level, a combination of field and modelled data is used to present the nation-wide picture for water quality.

It is too costly to monitor the thousands of river reaches throughout New Zealand, and monitoring sites operated by regional councils and NIWA do not cover the full range of different river environments. Many sites tend to be situated downstream of more affected areas such as lowlands, towns and other intensive land uses, while in comparison more pristine areas and headwaters are relatively under-represented. As monitored water quality sites tend to focus on higher-impacted areas, aggregated results for the wider national picture can be biased towards those.

To fill the gaps where monitoring isn’t carried out, and give us a more representative picture of river condition across the whole country, models are used to estimate what the condition in unmonitored areas is likely to be. 

Modelling involves some degree of approximation. For example, the models can’t show the impacts of a specific point source discharge and won’t identify the effects of best practice land management in localised areas. However, they give a broad indication of water quality at unmonitored locations and, combined with data from monitored sites, provide the best available information for a national perspective on river condition.  If you’re interested in a particular site we suggest you use the Explore Data section to find the nearest monitoring sites and see the latest state and trend results for Rivers.  Alternatively you can use the LAWA map to navigate to River Quality sites by selecting 'River Quality' from the 'Show me...' drop down menu.


MfE are working with regional councils and NIWA to improve the consistency and representativeness of the monitoring network across a range of New Zealand’s river environments.